Clinical Significance:
Octreotide (Sandostatin,® Novartis Pharmaceutical Company) is used for the control of symptoms associated with functional neuroendocrine tumors. Frequent measurement of the octreotide levels may be useful in guiding therapy in patients with poorly controlled symptoms or those patients experiencing tumor growth during LAR therapy. Octreotide levels in blood need to be in a specific range to be effective. Measuring octreotide immediately prior to the monthly LAR injection will determine trough levels of the drug in your blood.
Reference Range:
Long-acting repeatable (LAR) dose-response levels: mean octreotide level A-} 2 SD for patients on octreotide LAR for 3 or more months (steady-state). The following represent trough levels measured immediately before an injection of LAR.
Octreotide administered by pump:
60 mg/month: 10,000 pg/ml +/- 2,500 pg/ml
30 mg/month: 5,000 pg/ml +/- 2,500 pg/ml
Octreotide administered as Sandostatin(R) LAR:
120 mg/month: 9,000 pg/ml +/- 2,000 pg/ml
60 mg/month: 5,000 pg/ml +/- 2,000 pg/ml
30 mg/month: 2,500 pg/ml +/- 1,500 pg/ml
Octreotide administered by subcutaneous injection:
Measurement of plasma octreotide is not recommended for individuals using multiple daily octreotide injections due to the short half life of octreotide in the plasma (approximately 90-120 minutes)
Procedure:
Octreotide is measured by direct radioimmunoassay. There is no cross-reactivity with native somatostatin-14 or somatostatin-28. The also is no cross-reactivity with lanreotide, and this test should not be used to measure blood levels of this drug.
Patient Preparation:
This test is useful only for those patients being treated with octreotide acetate. No special preparation is needed for this test. For optimal results, blood for this test should be drawn immediately before the patient’s next injection of octreotide LAR (trough levels).
Specimen Collection:
Collect 3mL serum or EDTA plasma and separate as soon as possible. Octreotide is stable at room temperature for 3 days. Specimens can be stored room temperature, refrigerated, or frozen in dry ice. Minimum specimen size is 1mL.
Special Specimens:
For tumor/tissue and various fluids (e.g., CSF, peritoneal fluid, synovial fluid) contact ISI for requirements and special handling instructions.
Shipping Instructions:
Specimens can be shipped at ambient temperature, refrigerated, or frozen in dry ice.
References:
1. Anthony L, Vinik AI. Evaluating the characteristics and the management of patients with neuroendocrine tumors receiving octreotide LAR during a 6-year period. Pancreas.2011;40:987-94.
2. Woltering EA, Mamikunian PM, Zietz S, et al. The effect of octreotide LAR dose and weight on octreotide blood levels in patients with neuroendocrine tumors. Pancreas. 2005;31(4):392-400.
3. Woltering EA, Salvo VA, O’Dorisio TM, et al. Clinical value of monitoring plasma octreotide levels during chronic octreotide long-acting repeatable therapy in carcinoid patients. Pancreas. 2008;Jul;37(1):94-100.
4. Woltering EA, Hilton RS, Zolfoghary CM, et al. Validation of serum versus plasma measurements of chromogranin a levels in patients with carcinoid tumors: lack of correlation between absolute chromogranin a levels and symptom frequency. Pancreas. 2006;Oct;33(3):250-4.